A Long-Term Evolution (LTE) system offers high peak data rates, low latency, improved system capacity, and low operating cost resulting from simple network architecture. An LTE system also provides seamless integration to older wireless network, such as GSM, CDMA and Universal Mobile Telecommunication System (UMTS). In LTE systems, an evolved universal terrestrial radio access network (E-UTRAN) includes a plurality of evolved Node-Bs (eNodeBs or eNBs) communicating with a plurality of mobile stations, referred as user equipments (UEs). Enhancements to LTE systems are considered so that they can meet or exceed International Mobile Telecommunications Advanced (IMT-Advanced) fourth generation (4G) standard. Multiple access in the downlink is achieved by assigning different sub-bands (i.e., groups of subcarriers, denoted as resource blocks (RBs)) of the system bandwidth to individual users based on their existing channel condition. In LTE networks, Physical Downlink Control Channel (PDCCH) is used for dynamic downlink scheduling.
A plurality of physical resource blocks (PRBs) is allocated for PDCCH transmission that carry downlink control information (DCI). In order to decode PDCCH targeted specifically to a UE, the UE needs to find out where its PDCCH is. In the so-called “blindly” decoding process, the UE must try a number of candidate PDCCHs before knowing which PDCCH is targeted for itself. The allocated radio resources of the candidate PDCCHs may be distributed or localized. In addition, the PDCCHs may constitute a common search space (CSS) or a UE-specific search space (UESS). As a result, supporting both distributed and localized PDCCH transmission in both common and UE-specific search spaces for each UE may result in excessive control signaling and increased number of blind decoding.
The signal bandwidth for next generation 5G new radio (NR) systems is estimated to increase to up to hundreds of MHz for below 6 GHz bands and even to values of GHz in case of millimeter wave (mmWave) bands. Furthermore, the NR peak rate requirement can be up to 20 Gbps, which is more than ten times of LTE. Three main applications in 5G NR system include enhanced Mobile Broadband (eMBB), Ultra-Reliable Low Latency Communications (URLLC), and massive Machine-Type Communication (MTC) under milli-meter wave technology, small cell access, and unlicensed spectrum transmission. Multiplexing of eMBB & URLLC within a carrier is also supported. Specifically, the mmWave frequency spectrum between 3G and 300 GHz is explored for the next generation broadband cellular communication networks. The mmWave wireless network uses directional communications with narrow beams and can support multi-gigabit data rate. Directional antenna can be implemented by phased array with many antenna elements. Analog beamforming and spatial multiplexing methods can be applied in multiple antenna systems.
A solution to improve the design of PDCCH structure and to support analog beamforming, COMP, and MU-MIMO in PDCCH design is sought.